Granulomatosis with polyangiitis (Wegener's) (GPA) and microscopic polyangiitis (MPA) are two rare immune system disorders that cause the inflammation of blood vessels, or vasculitis. In order to properly treat these diseases, it is critical that the level of disease activity can be determined over the course of the disease. The purpose of this study is to determine new biological markers, or biomarkers, that may be used to assess the severity of disease in people with GPA or MPA.